I know it's fun to buy and install new stuff, but is there any reason why you can't just use an equaliser to do what any tube does? Is there any measurement that would favor a tube that gives extra bass vs EQ'ing up the bass?
When people say a tube gives extra "micro detail" don't they just mean that it ups the treble a bit? Why not just EQ up the treble? Potentially big $$$ for these rare tubes vs nothing for an EQ.